1. Field of the Invention
The present invention relates to a surface light source device and a liquid crystal display device having the surface light source device. More particularly, the present invention relates to a surface light source device capable of enhancing a luminance and a liquid crystal display device having the surface light source device.
2. Description of the Related Art
Generally, a liquid crystal display (LCD) device displays an image by varying an optical transmittance of liquid crystal. The LCD device has many advantages, which make the LCD device popular for use in various fields. Some examples of advantages of the LCD device include a thin thickness, a lightweight, a low power consumption, a low driving voltage, etc.
The LCD device includes a liquid crystal display panel that converts light into images, and a light source device that provides the liquid crystal display panel with light. A conventional light source device employs a cold cathode fluorescent lamp (CCFL) that has a cylindrical shape. The conventional light source device is classified as either an edge illumination type or direct illumination type according to a position of the CCFL.
In the edge illumination type light source device, the CCFL is disposed at a side portion of a light guide plate, so that light generated from the CCFL enters the light guide plate through a side face of the light guide plate. Light then exits the light guide plate through an upper face of the light guide plate.
In the direct illumination type, a plurality of CCFLs are disposed below the liquid crystal display panel, and a diffusion plate is disposed between the CCFLs and the liquid crystal display panel.
Use of either the light guide plate or the diffusion plate decreases light utilization efficiency of the convention light source device. Additionally, use of either the light guide plate or the diffusion plate increases manufacturing cost for the LCD device, and uniformity of luminance is still low.
In order to solve above-mentioned problems, a surface light source device has been developed. The surface light source device includes a light source body and electrodes. The light source body has an internal space divided into discharge spaces. The electrodes receive a discharge voltage that creates a potential difference across the light source body, which is sufficient to induce an electrical discharge of a discharge gas in the discharge spaces. The discharge spaces are connected to each other so that the discharge gas is uniformly distributed in the discharge spaces. The electrical discharge of the discharge gas generates ultraviolet light that may be converted into visible light.
The surface light source device includes a light reflecting layer formed in the light source body. The light reflecting layer reflects light toward the liquid crystal display panel. Generally, the light reflecting layer includes, but is not limited to, polyethylene terephthalate (PET) or metal.
Manufacturing processes for the surface light source device include a process performed at a temperature higher than about 500 F. At such a high temperature, when the light reflecting layer is formed in the light source body, the light reflecting layer may be deformed by heat during the manufacturing process. Such heat deformation may prevent the light reflecting layer from operating normally. Thus it is desirable to produce a light reflecting layer that is not deformed by heat and has a high reflectivity.